Increasing apprehension and concern for environmental and life forms evolution, industrial emissions, earlier medical diagnostics, and public and food safety, among other factors, have raised demand for higher level of sensitivity detection and monitoring of vital chemical and biological species in extremely low concentrations. Advances in nanostructured materials have enabled the emergence of a new generation of ultra-sensitive solid-state sensors having a high surface-to-volume ratio, high porosity, and exceptional chemical properties. Due to limitations in the structures and materials used in such sensors, however, the detection limit is typically in parts per million (PPM). As advances continue to be made in this technology, more focused detection limits may be desired.